高通平台开发系列讲解（USB篇）adb应用adbd分析

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在apps_proc/system/core/adb/adb_main.cpp文件中main()函数会调用adb_main()函数，然后调用uab_init函数
在uab_init（）函数中，会创建一个线程，在线程中会调用init_functionfs（）函数，利用ep0控制节点，创建ep1、ep2输入输出节点

目录：​​apps_proc/system/core/adb/usb_linux_client.cpp​​

#define USB_FFS_ADB_EP0   USB_FFS_ADB_EP(ep0)
#define USB_FFS_ADB_OUT   USB_FFS_ADB_EP(ep1)
#define USB_FFS_ADB_IN    USB_FFS_ADB_EP(ep2)
 
 
static void init_functionfs(struct usb_handle *h)
{
    ssize_t ret;
    struct desc_v1 v1_descriptor;
    struct desc_v2 v2_descriptor;
 
    v2_descriptor.header.magic = cpu_to_le32(FUNCTIONFS_DESCRIPTORS_MAGIC_V2);
    v2_descriptor.header.length = cpu_to_le32(sizeof(v2_descriptor));
    v2_descriptor.header.flags = FUNCTIONFS_HAS_FS_DESC | FUNCTIONFS_HAS_HS_DESC |
                                 FUNCTIONFS_HAS_SS_DESC;
    v2_descriptor.fs_count = 3;
    v2_descriptor.hs_count = 3;
    v2_descriptor.ss_count = 5;
    v2_descriptor.fs_descs = fs_descriptors;
    v2_descriptor.hs_descs = hs_descriptors;
    v2_descriptor.ss_descs = ss_descriptors;
 
    if (h->control < 0) { // might have already done this before
        D("OPENING %s\n", USB_FFS_ADB_EP0);
        h->control = adb_open(USB_FFS_ADB_EP0, O_RDWR);
        if (h->control < 0) {
            D("[ %s: cannot open control endpoint: errno=%d]\n", USB_FFS_ADB_EP0, errno);
            goto err;
        }
 
        ret = adb_write(h->control, &v2_descriptor, sizeof(v2_descriptor));
        if (ret < 0) {
            v1_descriptor.header.magic = cpu_to_le32(FUNCTIONFS_DESCRIPTORS_MAGIC);
            v1_descriptor.header.length = cpu_to_le32(sizeof(v1_descriptor));
            v1_descriptor.header.fs_count = 3;
            v1_descriptor.header.hs_count = 3;
            v1_descriptor.fs_descs = fs_descriptors;
            v1_descriptor.hs_descs = hs_descriptors;
            D("[ %s: Switching to V1_descriptor format errno=%d ]\n", USB_FFS_ADB_EP0, errno);
            ret = adb_write(h->control, &v1_descriptor, sizeof(v1_descriptor));
            if (ret < 0) {
                D("[ %s: write descriptors failed: errno=%d ]\n", USB_FFS_ADB_EP0, errno);
                goto err;
            }
        }
 
        ret = adb_write(h->control, &strings, sizeof(strings));
        if (ret < 0) {
            D("[ %s: writing strings failed: errno=%d]\n", USB_FFS_ADB_EP0, errno);
            goto err;
        }
    }
 
    h->bulk_out = adb_open(USB_FFS_ADB_OUT, O_RDWR);
    if (h->bulk_out < 0) {
        D("[ %s: cannot open bulk-out ep: errno=%d ]\n", USB_FFS_ADB_OUT, errno);
        goto err;
    }
 
    h->bulk_in = adb_open(USB_FFS_ADB_IN, O_RDWR);
    if (h->bulk_in < 0) {
        D("[ %s: cannot open bulk-in ep: errno=%d ]\n", USB_FFS_ADB_IN, errno);
        goto err;
    }
 
    return;
 
err:
    if (h->bulk_in > 0) {
        adb_close(h->bulk_in);
        h->bulk_in = -1;
    }
    if (h->bulk_out > 0) {
        adb_close(h->bulk_out);
        h->bulk_out = -1;
    }
    if (h->control > 0) {
        adb_close(h->control);
        h->control = -1;
    }
    return;
}

bulk_write和bulk_read会调用adb_write读写bulk_in和bulk_out节点，而usb_ffs_write和usb_ffs_read会调用bulk_write和bulk_read

目录：​​apps_proc/system/core/adb/usb_linux_client.cpp​​

static int bulk_write(int bulk_in, const uint8_t* buf, size_t length)
{
    size_t count = 0;
    int ret;
 
    do {
        ret = adb_write(bulk_in, buf + count, length - count);
        if (ret < 0) {
            if (errno != EINTR)
                return ret;
        } else {
            count += ret;
        }
    } while (count < length);
 
    D("[ bulk_write done fd=%d ]\n", bulk_in);
    return count;
}
 
static int usb_ffs_write(usb_handle* h, const void* data, int len)
{
    D("about to write (fd=%d, len=%d)\n", h->bulk_in, len);
    int n = bulk_write(h->bulk_in, reinterpret_cast<const uint8_t*>(data), len);
    if (n != len) {
        D("ERROR: fd = %d, n = %d: %s\n", h->bulk_in, n, strerror(errno));
        return -1;
    }
    D("[ done fd=%d ]\n", h->bulk_in);
    return 0;
}

在usb_ffs_init会注册usb_handle的读写函数:

目录：​​apps_proc/system/core/adb/usb_linux_client.cpp​​

static void usb_ffs_init()
{
    D("[ usb_init - using FunctionFS ]\n");
 
    usb_handle* h = reinterpret_cast<usb_handle*>(calloc(1, sizeof(usb_handle)));
    if (h == nullptr) fatal("couldn't allocate usb_handle");
 
    h->write = usb_ffs_write;
    h->read = usb_ffs_read;
    h->kick = usb_ffs_kick;
    h->control = -1;
    h->bulk_out = -1;
    h->bulk_out = -1;
 
    adb_cond_init(&h->notify, 0);
    adb_mutex_init(&h->lock, 0);
 
    D("[ usb_init - starting thread ]\n");
    adb_thread_t tid;
    if (adb_thread_create(&tid, usb_ffs_open_thread, h)){
        fatal_errno("[ cannot create usb thread ]\n");
    }
}

而usb_write和usb_read又会调用usb_handle的读写函数

目录：​​apps_proc/system/core/adb/usb_linux_client.cpp​​

int usb_write(usb_handle *h, const void *data, int len)
{
    return h->write(h, data, len);
}
 
int usb_read(usb_handle *h, void *data, int len)
{
    return h->read(h, data, len);
}
int usb_close(usb_handle *h)
{
    return 0;
}
 
void usb_kick(usb_handle *h)
{
    h->kick(h);
}

remote_read和remote_write又调用了usb_read和usb_write，而最终在transport_usb.cpp文件中，调用init_usb_transport（）函数，注册到atransport结构体中的读写函数